Method of producing magnetic core parts

ABSTRACT

In a method of producing at least two separate magnetic core parts that are each made up of stacked laminations, the following steps are provided: the step of stamping sections out of an individual metal sheet to form connecting struts located between and extending transversely to lamination sections of the sheet, and the step of displacing the lamination sections toward each other in a longitudinal direction of the lamination sections for shearing the struts so as to separate the lamination sections from one another. Also, a blank for performing steps in a method of producing at least two separate magnetic core parts that are each made up of stacked laminations. The blank includes a sheet of metal having a longitudinal axis and having at least one opening having a longitudinal axis, the opening being located in the sheet so that the axes are mutually perpendicular. The sheet also has two notches extending inwardly transverse to the axis of the sheet from respective sides thereof and the opening is adjacent the notches to form struts therebetween.

[ Dec. 18, 1973 METHOD OF PRODUCING MAGNETIC CORE PARTS [75] Inventors: Erwin Bock; Oskar Theml, both of Amberg, Germany [73] Assignee: Siemens Aktiengesellschaft, Berlin and Munich, Germany [22] Filed: Nov. 29, 1971 [21] Appl. No.: 202,881

[30] Foreign Application Priority Data Dec. 1, 1970 Germany P 20 59 064.1

[52] U.S. Cl 29/609, 29/416, 29/418, 29/521 [51] Int. Cl. H0lf 7/06 [58] Field of Search 29/609, 602, 416, 29/418, 434, 412, 413, 521

[56] References Cited UNITED STATES PATENTS 2,724,867 ll/l955 Smith 29/418 X 3,122,880 3/1964 Greiner..... 29/4l3 X 3,571,920 3/1971 Berg 29/413 X 3,624,896 l2/l97l Daubeney.... 29/416 X 3,694,903 l0/l972 Deming 29/609 X 3,453,715 7/1969 Rogers 29/416 Primary ExaminerCharles W. Lanham Assistant ExaminerCarl E. Hall AttorneyArthur E. Wilfond et al.

[5 7 ABSTRACT In a method of producing at least two separate magnetic core parts that are each made up of stacked laminations, the following steps are provided: the step of stamping sections out of an individual metal sheet to form connecting struts located between and extending transversely to lamination sections of the sheet, and the step of displacing the lamination sections toward each other in a longitudinal direction of the lamination sections for shearing the struts so as to separate the lamination sections from one another.

Also, a blank for performing steps in a method of producing at least two separate magnetic core parts that are each made up of stacked laminations. The blank includes a sheet of metal having a longitudinal axis and having at least one opening having a longitudinal axis, the opening being located in the sheet so that the axes are mutually perpendicular. The sheet also has two notches extending inwardly transverse to the axis of the sheet from respective sides thereof and the opening is adjacent the notches to form struts therebetween.

3 Claims, 5 Drawing Figures METHOD OF PRODUCING MAGNETIC CORE PARTS The invention relates to a method of producing divided magnetic core parts of stacked metal sheets or laminations. In electro-magnetic switching devices, it is necessary, particularly for U-shaped magnets, to assemble the U member from two angles between which a defined air gap must be provided as a remanence air gap. This had been accomplished in a manner such that the L or angularly shaped individual sheets were punched out and thereafter packaged according to the desired number of individual laminations. Two magnetic core portions stacked in this way were then positioned mutually adjacent and separated from each other by an air gap and and were connected with each other by a cover sheet held by rivets. Aside from the expense of making two stackings, this production method had the disadvantage that the tolerance in the sheet thickness could be at the upper limit in the sheets of one part of the magnet core and, at the lower limit, for the sheets of the other part of the magnet core. As a result, the magnet core parts were of variable thickness and this had a detrimental effect at least during pressing when the entire magnet core was riveted.

It is an object of the invention to provide steps in a method of producing at least two separate magnetic core parts that are each made of stacked laminations. Subsidiary to this object, it is an object of the invention to provide such a method which takes into account the thickness tolerances of the rolled sheets with which the core parts are stacked insofar that the maximum deviation thickness will correspond to the continuous rolling deviation of the sheets.

It is still another object of the invention to provide method steps which will simplify the method of stacking laminations still further.

It is a further object of the invention to provide a blank for performing steps in a method of producing at least two separate magnetic core parts that are each made up of stacked laminations.

According to a feature of the method of the invention, individual sheets, each of which corresponds to at least two magnet core parts are punched to have thin joining struts extending essentially transversely to the longitudinal direction of the magnet core parts. The joining struts are sheared off by shifting the individual sections toward each other in the longitudinal direction of the magnetic core parts. In order to make it unnecessary to shear off each sheet individually, it is preferable to effect the shearing after the individual sheets have been packaged.

A preferred blank for performing the method of the invention was found to be one which contains at least one trapezoidal opening whose longitudinal axis is essentially transverse to the longitudinal axis of the blank. Also, at least portions of at least one other trapezoidal opening have substantially the same shape as the firstmentioned opening, each of the additional openings having two mutually parallel bases and a non-parallel side. The two additional openings are disposed in the sheet such that their short bases and the short base of the first-mentioned opening lie on mutually adjacent parallel lines, respectively. Struts separating the additional openings from the first-mentioned openings are located substantially in the extension lines of the nonparallel sides of the first-mentioned opening and of the respective non-parallel sides of the additional openings.

This embodiment of the blank is especially preferable because it allows main-taining an essentially uniform air gap in a simple manner.

It is particularly expedient for shearing in a simple manner, if the width of the connecting struts corresponds approximately to the sheet thickness. Dimensioning the magnetically effective air gap width is particularly simple when the length of the longitudinal side of an opening amounts to about the entire width of the sheet less twice the sheet thickness, that is, the remaining remnant parts must not bend.

According to another embodiment of the blank, the depth and inclination of the non-parallel sides of the trapezoidal opening is selected so that when the individual lamination sections are sheared off, an air gap width can be adjusted which will remain constant over the entire air gap length.

Although the invention is illustrated and described herein as a method for producing magnetic core parts, it is nevertheless not intended to be limited to the details shown, since various modifications may be made therein within the scope and the range of the claims.

The invention, however, together with additional objects and advantages, will be best understood from the following description and in connection with the accompanying drawings in which:

FIG. 1 illustrates a blank comprising two mutually connected individual metal sheet sections having connecting struts extending transversely to the direction of separation;

FIG. 2 illustrates the individual lamination sections of FIG. 1 after being sheared;

FIG. 3 shows another embodiment of a blank in the form of a punched sheet having trapezoidal openings;

FIG. 4 is a punched sheet similar to the blank of FIG. 3 and comprises only one trapezoidal opening which extends almost over its entire width; and

FIG. 5 shows the punched sheet of FIG. 4 with the connecting struts sheared off.

The same parts in the different FIGS. are given the same reference numerals.

In the embodiment of FIG. 1, one of the U-shaped metal sheets 1 with which the magnetic core parts are stacked is shown comprising two individual lamination sections 2 and 3 which are substantially L-shaped. The individual sections 2 and 3 are connected via struts 4 and 5 which extend essentially perpendicularly to the longitudinal direction of the sheet l or, more precisely, transversely to the bight portion of the composite U- shapd member. The connecting struts 4 and 5 are formed by providing rectangular openings 6, 7 and 8.

The connected individual sections 2 and 3 are punched in the form seen in FIG. 1 to form a blank. The sections are then placed into the position shown in FIG. 2 by applying pressure as indicated by the arrows in FIG. I. An insulating foil 9 corresponding to the air gap width is inserted between the individual sheets 2 and 3 and keeps the sheets 2 and 3 spaced at an appropriate distance.

The connecting struts 4 and 5 are severed so that a magnetic shunt is precluded. In order to be able to more or less completely discount the remnant ends 10 and 11 of the connecting struts 4 and 5, a punched sheet section, shown in FIG. 3, is advantageously used. The connecting struts l2 serve here as connecting members for trapezoidal openings 13, 14, or parts thereof, which are denoted by reference numeral 15.

The trapezoidal openings are disposed with their longitudinal axes transversely to the longitudinal axis of the magnetic core, which is indicated in FIG. 3 with a dashed line 16. The short longitudinal sides or bases 17 of the trapezoids face each other. The connecting struts 12 are positioned substantially in the extension lines of two non'parallel sides 18,19 of the trapezoidal openings, so that the aforementioned ends 10,11 are virtually non-existent.

FIG. shows how the shearing locations 20 become positioned when the individual lamination sections 2 and 3 are pushed together. In the embodiment of FIG. 4 and also FIG. 5, the longer longitudinal base 21 of the trapezoidal opening 22 is present in the predominant part of the total width of the individual sections 2 and 3, so that the remaining residual portions 23 have hardly any effect on the determination of the magnetic air gap. The remaining portions 23 may also have a great air gap width relative to the air gap 24 corresponding to the large longitudinal side 21. The width of the air gap 24 is again determined by an inserted foil. The embodiment of FIG. 4 has the advantage that work may be conducted with a relatively large-area punching stamp so that the stamp has a relatively good service life.

The embodiment of FIGS. 4 and 5 does not afford an effective air gap length enlarged relative to the perpendicular to both individual sections 2, 3 so that, as mentioned previously, the remnant parts 23 can provide a larger air gap. This, however, affords the advantage of connecting both magnetic core parts which are assembled from the individual sections 2 and 3, by casting the dove tail connections of at least the residual portions 23 of the total air gap.

Generally, however, the magnet core parts comprising individual sections 2 and 3 are riveted together through mounted-on cover sheets such that the lamination sections 2, 3 are at a spacing determined by the inserted foil.

Additional reinforcement can be obtained by dipping the interconnected magnetic core parts into casting resin and thereby cementing the dove-tail connection. In this respect alone, the embodiment according to FIGS. 3 to 5 is preferable to the embodiment of FIGS. 1 and 2.

We claim:

1. A method of producing magnetic core parts of stacked laminations comprising the steps of stamping sections out of a plurality of metal sheets each having a longitudinal axis to form laminations, each lamination having first and second portions connected to each other by struts extending transversely to the longitudinal axis of the sheets, placing the laminations one upon the other with said first and second portions aligned to form a stack of said laminations, and displacing said first and second portions toward each other in said longitudinal direction to shear the struts and sever said portions from one another.

2. A method as claimed in claim 1, wherein the laminations stamped from the sheets have openings and notches, the openings being adjacent the notches to form the struts therebetween.

3. A method as claimed in claim 2, wherein the notches define a plunger-like projection in one of the portions and the opening defines a cutout in the other one of the portions, the cutout being opposite the projection in the longitudinal direction, the struts extending laterally of the projection to the longitudinal sides a of the cutout, respectively, and displacing the portions toward each other in the longitudinal direction to shear the struts by inserting the projection into the cutout. 

1. A method of producing magnetic core parts of stacked laminations comprising the steps of stamping sections out of a plurality of metal sheets each having a longitudinal axis to form laminations, each lamination having first and second portions connected to each other by struts extending transversely to the longitudinal axis of the sheets, placing the laminations one upon the other with said first and second portions aligned to form a stack of said laminations, and displacing said first and second portions toward each other in said longitudinal direction to shear the struts and sever said portions from one another.
 2. A method as claimed in claim 1, wherein the laminations stamped from the sheets have openings and notches, the openings being adjacent the notches to form the struts therebetween.
 3. A method as claimed in claim 2, wherein the notches define a plunger-like projection in one of the portions and the opening defines a cutout in the other one of the portions, the cutout being opposite the projection in the longitudinal direction, the struts extending laterally of the projection to the longitudinal sides of the cutout, respectively, and displaCing the portions toward each other in the longitudinal direction to shear the struts by inserting the projection into the cutout. 